Blade damping device



Ap 1954 'r. G. WOODWELL BLADE DAMPING DEVICE Filed July 6, 1962 FIG. 4

- INVENTOR THORNTON 6; WOODWELL 8V 02,4104 Q ATTORNEY I United States Patent Office ,7 3,129,921 Patented Apr. 21, 1964 3,129,921 BLADE DING DEVICE Thornton G. Woodweli, West Hartford, Conn., assignor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Filed July 6, 1962, Ser. No. 207,929 9 Claims. (*Cl. 253-77) This invention relates to a blade damping device.

One feature of the invention is a damping device adapted for attachment to one side of a row of compressor or turbine blades. Another feature is a device of this character which becomes increasingly effective with an increase in the speed of the disc carrying the blades.

Another feature is a damper which is readily attached to an existing rotor construction without substantial modification of the blades. Another feature is a damper particularly adapted for use with the so-called extended roottype of blade.

Other features and advantages will be apparent from the specification and claims, and from the accompanying drawings which illustrate an embodiment of the invention.

FIG. 1 is a fragmentary view in elevation of a portion of a rotor incorporating the invention.

FIG. 2 is a sectional view substantially along the line 2-2 of FIG. 1.

FIG. 3 is a perspective view of a damper element and the adjacent structures.

FIG. 4 is a fragmentary sectional view along the line 44 of FIG. 2.

FIG. 5 is a sectional view substantially along the line 55 of FIG. 2.

The invention is shown in connection with a rotor con struction in which a disc 2 has axial grooves 4 in the periphery to receive the blade root or fastening 6 shown in the shape of a dovetail and located at the inner end of the blade element 8. The blade element includes the dovetail portion 6, a radially projecting root extension 10 extending outwardly from the dovetail portion, an operative blade portion 12 at the outer end of the element, and a blade platform 14 positioned between the root extension and the operative blade portion. In this arrangement it will be clear that the periphery 16 of the disc is spaced radially inward from the platform 14, as best shown in FIG. 1. The plurality of blade elements are thus arranged in a circumferential row in spaced relation to one another and form with the disc a rotor which may be utilized in either a compressor or turbine.

The platforms 14 of adjacent blades are in closely spaced relation to one another, as best shown in FIGS. 4 and 5, such that each blade may vibrate circumferentially to some extent, independently of each other blade. The purpose of the present invention is to control the vibratory movement of the individual blades.

The blades are retained in position on the periphery of the disc by end plates 18 and 20 attached as by rivets 22 to opposite sides of the disc adjacent the periphery. The disc 18 extends far enough to reach the blade platform and form a closure for the spaces between the root extensions. The plate 249 is especially designed to form a part of the damper structure embodying the present invention, as will appear hereinafter.

Each blade is damped by an individual blade damping element 24 which has a base portion 26 having a circumferentially extending surface 28 thereon to engage with the inner surface of a lug 30 on the inside of the plate 20. The surfaces 28 of the several damping elements are all located at the same distance from the center of the disc so that the several lugs 30 form an interrupted cylindrical flange on the inside of the plate 20. The lugs are carried by integral fingers 31 forming a part of the coverplate. Projecting from the base 26 of the damping element is an arm 32 which extends radially outward beyond the lug 30 and also obliquely with respect to the radius for engagement with the platform 14 of one of the blades. The arm 32 terminates in a circumferentially extending surface 34 which engages the underside of the platform 14 and by frictional engagement therewith will reduce the vibratory motion of the blade. The circumferential dimension of the surface 34 is preferably slightly less than the circumferential dimension of the blade platform and the circumferential dimension of the arm 32 is so selected that the arms 32 on adjacent blade dampers Will not be in contact.

The integral radially extending fingers 31 on the plate 20 are spaced apart circumferentially and terminate at a point radially outward beyond the lug 39, thus these fingers serve to hold the damping elements in position against the end surfaces of the root extensions and in the proper position to engage effectively with the lug 3t) and blade platform 14. The lugs 39 serve to locate the damper elements circumferentially as best shown in FIG. 5 thus making sure that each damper is in engagement with the respective lug and blade platform. It will be noted that the circumferential dimension of the bases 26 of the blade damping elements is such that adjacent elements are spaced apart to some extent so that each damper is free to move circumferentially to a limited degree so that frictional damping can occur between the surface 28 and the lug 30.

The radial load on the end plate 24 resulting from the action of the blade dampers is carried in part by a circumferentially extending flange 38 on the inner end of the plate 20 engaging with a notch 4% on the disc. The plate 20 may also have another circumferential flange 42 which carries sealing fins 44.

In operation the blade dampers are free to move to a limited extent in a radial direction. As the rotor is spun, centrifugal force will urge the dampers radially outward bringing the surfaces 23 and 34 into contact with the lug 30 and platform 14, respectively. By appropriate selection of damper dimensions the damper can be so arranged that a greater force is exerted by the surface 28 than by the surface 34, such that, with equal friction coefiicients, damping will occur by relative motion between the damper and the blade platform. Obviously, the higher the speed of the rotor, the greater the pressure applied on these two surfaces and, accordingly, the more effective the damping action. The blade dampers may have obliquely positioned surfaces 46 at their inner edges to engage with a similarly inclined surface 48 on the plate 20 to limit the free radial movement of the blade dampers with respect to the coverplate.

It is to be understood that the invention is not limited to the specific embodiment herein illustrated and described, but may be used in other ways without departure from its spirit as defined by the following claims.

I claim:

1. A rotor construction for compressors or turbines including a disc, a row of blades mounted on and extending substantially radially from the periphery of the disc, each blade presenting a circumferentially extending surface and having a platform thereon, said blades having end surfaces in a radial plane, a coverplate for attachment to one side of the disc in overlying relation to a part of each of the blades, and damping means including a plurality of circumferentially spaced lugs on the inside of the coverplate, and damping elements, one for each blade, positioned in part between the coverplate and the end surfaces of the blades and guided by said coverplate and said end surfaces of the blades for substantially radial movement under centrifugal force, each element having a surface frictionally engaging with one of said lugs and another surface frictionally engageable with the surface on the platform on one of the blades.

2. A device as in claim 1 in which the damping elements are limited in radially outward movement only by contact of said two surfaces therein with the associated lug and platform.

3. A device as in claim 1 in which the lug engaging surface on each element is offset circumferentially of the coverplate from the platform engaging surface.

4. A device as in claim 1 in which the lugs are mounted on radially extending fingers integral with the coverplate.

5. In a compressor or turbine rotor, the combination with a disc, and a plurality of cireumferentially spaced blades mounted in a row on the periphery of the disc and projecting substantially radially therefrom, of a damper device for the blades including a coverplate attached to and overlying one side of the disc adjacent the periphery, said coverplate having a plurality of circumferentially spaced lugs thereon corresponding in spacing to the blades, and a plurality of damper elements, one for each blade, positioned between the row of blades and the coverplate, each damper element having a circumferentially extending surface engaging with one of the lugs and another radially and circumferentially spaced surface extending in a circumferential direction and engaging with a circumferential surface on one of the blades, each damper element being supported in a radially outward direction solely by the lug and circumferential surface on the blade such that, when the disc is rotated, the

damper is urged by centrifugal force against the lug and surface.

6. The combination as in claim 5 in which each blade has a circumferentially extending platform located radially between the inner and outer ends of the blade and providing the circumferential surface engaged by the damper element.

7. The combination as in claim 6 in which each blade has a root fitting in a slot in the blade periphery and a radially projecting root extension between the root and the platform and the coverplate overlies these root extensions.

8. The combination as in claim 5 in which the lugs are carried by radially extending fingers on the periphery of the co erplate.

9. The combination as in claim 7 in which root extensions for the blades have radially extending end surfaces all substantially in a radial plane and the damper elements are positioned between the radially extending end surfaces of the root extensions and the coverplate.

References Cited in the file of this patent UNITED STATES PATENTS 2,660,400 Grifiith Nov. 24, 1953 2,935,297 Stalker May 3, 1960 2,999,668 Howald et al Sept. 12, 1961 FOREIGN PATENTS 667,979 Great Britain Mar. 12, 1952 212,964 Australia Feb. 18, 1958 226,940 Australia Sept. 18, 1958 

1. A ROTOR CONSTRUCTION FOR COMPRESSORS OR TURBINES INCLUDING A DISC, A ROW OF BLADES MOUNTED ON AND EXTENDING SUBSTANTIALLY RADIALLY FROM THE PERIPHERY OF THE DISC, EACH BLADE PRESENTING A CIRCUMFERENTIALLY EXTENDING SURFACE AND HAVING A PLATFORM THEREON, SAID BLADES HAVING END SURFACES IN A RADIAL PLANE, A COVERPLATE FOR ATTACHMENT TO ONE SIDE OF THE DISC IN OVERLYING RELATION TO A PART OF EACH OF THE BLADES, AND DAMPING MEANS INCLUDING A PLURALITY OF CIRCUMFERENTIALLY SPACED LUGS ON THE INSIDE OF THE COVER- 